I'm pretty sure that engine was designed for lower octane fuel.
What you get from using higher octane racing fuel is resistance to detonation due to poor tuning decisions.
What you get best from racing fuel is a consistant platform from which to tune.
Pump gas is all over the place. Ethanol content changes, in California additiives change depending on time of year. A starting tune up one week may be diferent a few weeks later as pump gas is always changing.